DESCRIPTION

dig is a flexible tool for interrogating DNS name servers. It performs
DNS lookups and displays the answers that are returned from the name
server(s) that were queried. Most DNS administrators use dig to
troubleshoot DNS problems because of its flexibility, ease of use and
clarity of output. Other lookup tools tend to have less functionality
than dig.
Although dig is normally used with command-line arguments, it also has
a batch mode of operation for reading lookup requests from a file. A
brief summary of its command-line arguments and options is printed when
the -h option is given. Unlike earlier versions, the BIND 9
implementation of dig allows multiple lookups to be issued from the
command line.
Unless it is told to query a specific name server, dig will try each of
the servers listed in /etc/resolv.conf. If no usable server addresses
are found, dig will send the query to the local host.
When no command line arguments or options are given, dig will perform
an NS query for "." (the root).
It is possible to set per-user defaults for dig via ${HOME}/.digrc.
This file is read and any options in it are applied before the command
line arguments.
The IN and CH class names overlap with the IN and CH top level domain
names. Either use the -t and -c options to specify the type and class,
use the -q the specify the domain name, or use "IN." and "CH." when
looking up these top level domains.

SIMPLE USAGE

A typical invocation of dig looks like:
dig @server name type
where:
server
is the name or IP address of the name server to query. This can be
an IPv4 address in dotted-decimal notation or an IPv6 address in
colon-delimited notation. When the supplied server argument is a
hostname, dig resolves that name before querying that name server.
If no server argument is provided, dig consults /etc/resolv.conf;
if an address is found there, it queries the name server at that
address. If either of the -4 or -6 options are in use, then only
addresses for the corresponding transport will be tried. If no
usable addresses are found, dig will send the query to the local
host. The reply from the name server that responds is displayed.
name
is the name of the resource record that is to be looked up.
type
indicates what type of query is required -- ANY, A, MX, SIG, etc.
type can be any valid query type. If no type argument is supplied,
dig will perform a lookup for an A record.

OPTIONS

-4
Use IPv4 only.
-6
Use IPv6 only.
-b address[#port]
Set the source IP address of the query. The address must be a valid
address on one of the host's network interfaces, or "0.0.0.0" or
"::". An optional port may be specified by appending "#<port>"
-c class
Set the query class. The default class is IN; other classes are HS
for Hesiod records or CH for Chaosnet records.
-f file
Batch mode: dig reads a list of lookup requests to process from the
given file. Each line in the file should be organized in the same
way they would be presented as queries to dig using the
command-line interface.
-i
Do reverse IPv6 lookups using the obsolete RFC 1886 IP6.INT domain,
which is no longer in use. Obsolete bit string label queries (RFC
2874) are not attempted.
-k keyfile
Sign queries using TSIG using a key read from the given file. Key
files can be generated using tsig-keygen(8). When using TSIG
authentication with dig, the name server that is queried needs to
know the key and algorithm that is being used. In BIND, this is
done by providing appropriate key and server statements in
named.conf.
-m
Enable memory usage debugging.
-p port
Send the query to a non-standard port on the server, instead of the
default port 53. This option would be used to test a name server
that has been configured to listen for queries on a non-standard
port number.
-q name
The domain name to query. This is useful to distinguish the name
from other arguments.
-t type
The resource record type to query. It can be any valid query type.
If it is a resource record type supported in BIND 9, it can be
given by the type mnemonic (such as "NS" or "AAAA"). The default
query type is "A", unless the -x option is supplied to indicate a
reverse lookup. A zone transfer can be requested by specifying a
type of AXFR. When an incremental zone transfer (IXFR) is required,
set the type to ixfr=N. The incremental zone transfer will contain
the changes made to the zone since the serial number in the zone's
SOA record was N.
All resource record types can be expressed as "TYPEnn", where "nn"
is the number of the type. If the resource record type is not
supported in BIND 9, the result will be displayed as described in
RFC 3597.
-u
Print query times in microseconds instead of milliseconds.
-v
Print the version number and exit.
-x addr
Simplified reverse lookups, for mapping addresses to names. The
addr is an IPv4 address in dotted-decimal notation, or a
colon-delimited IPv6 address. When the -x is used, there is no need
to provide the name, class and type arguments. dig automatically
performs a lookup for a name like 94.2.0.192.in-addr.arpa and sets
the query type and class to PTR and IN respectively. IPv6 addresses
are looked up using nibble format under the IP6.ARPA domain (but
see also the -i option).
-y [hmac:]keyname:secret
Sign queries using TSIG with the given authentication key. keyname
is the name of the key, and secret is the base64 encoded shared
secret. hmac is the name of the key algorithm; valid choices are
hmac-md5, hmac-sha1, hmac-sha224, hmac-sha256, hmac-sha384, or
hmac-sha512. If hmac is not specified, the default is hmac-md5 or
if MD5 was disabled hmac-sha256.
NOTE: You should use the -k option and avoid the -y option, because
with -y the shared secret is supplied as a command line argument in
clear text. This may be visible in the output from ps(1) or in a
history file maintained by the user's shell.

QUERY OPTIONS

dig provides a number of query options which affect the way in which
lookups are made and the results displayed. Some of these set or reset
flag bits in the query header, some determine which sections of the
answer get printed, and others determine the timeout and retry
strategies.
Each query option is identified by a keyword preceded by a plus sign
(+). Some keywords set or reset an option. These may be preceded by the
string no to negate the meaning of that keyword. Other keywords assign
values to options like the timeout interval. They have the form
+keyword=value. Keywords may be abbreviated, provided the abbreviation
is unambiguous; for example, +cd is equivalent to +cdflag. The query
options are:
+[no]aaflag
A synonym for +[no]aaonly.
+[no]aaonly
Sets the "aa" flag in the query.
+[no]additional
Display [do not display] the additional section of a reply. The
default is to display it.
+[no]adflag
Set [do not set] the AD (authentic data) bit in the query. This
requests the server to return whether all of the answer and
authority sections have all been validated as secure according to
the security policy of the server. AD=1 indicates that all records
have been validated as secure and the answer is not from a OPT-OUT
range. AD=0 indicate that some part of the answer was insecure or
not validated. This bit is set by default.
+[no]all
Set or clear all display flags.
+[no]answer
Display [do not display] the answer section of a reply. The default
is to display it.
+[no]authority
Display [do not display] the authority section of a reply. The
default is to display it.
+[no]badcookie
Retry lookup with the new server cookie if a BADCOOKIE response is
received.
+[no]besteffort
Attempt to display the contents of messages which are malformed.
The default is to not display malformed answers.
+bufsize=B
Set the UDP message buffer size advertised using EDNS0 to B bytes.
The maximum and minimum sizes of this buffer are 65535 and 0
respectively. Values outside this range are rounded up or down
appropriately. Values other than zero will cause a EDNS query to be
sent.
+[no]cdflag
Set [do not set] the CD (checking disabled) bit in the query. This
requests the server to not perform DNSSEC validation of responses.
+[no]class
Display [do not display] the CLASS when printing the record.
+[no]cmd
Toggles the printing of the initial comment in the output
identifying the version of dig and the query options that have been
applied. This comment is printed by default.
+[no]comments
Toggle the display of comment lines in the output. The default is
to print comments.
+[no]cookie[=####]
Send a COOKIE EDNS option, with optional value. Replaying a COOKIE
from a previous response will allow the server to identify a
previous client. The default is +cookie.
+cookie is also set when +trace is set to better emulate the
default queries from a nameserver.
+[no]crypto
Toggle the display of cryptographic fields in DNSSEC records. The
contents of these field are unnecessary to debug most DNSSEC
validation failures and removing them makes it easier to see the
common failures. The default is to display the fields. When omitted
they are replaced by the string "[omitted]" or in the DNSKEY case
the key id is displayed as the replacement, e.g. "[ key id = value
]".
+[no]defname
Deprecated, treated as a synonym for +[no]search+[no]dnssec
Requests DNSSEC records be sent by setting the DNSSEC OK bit (DO)
in the OPT record in the additional section of the query.
+domain=somename
Set the search list to contain the single domain somename, as if
specified in a domain directive in /etc/resolv.conf, and enable
search list processing as if the +search option were given.
+dscp=value
Set the DSCP code point to be used when sending the query. Valid
DSCP code points are in the range [0..63]. By default no code point
is explicitly set.
+[no]edns[=#]
Specify the EDNS version to query with. Valid values are 0 to 255.
Setting the EDNS version will cause a EDNS query to be sent.
+noedns clears the remembered EDNS version. EDNS is set to 0 by
default.
+[no]ednsflags[=#]
Set the must-be-zero EDNS flags bits (Z bits) to the specified
value. Decimal, hex and octal encodings are accepted. Setting a
named flag (e.g. DO) will silently be ignored. By default, no Z
bits are set.
+[no]ednsnegotiation
Enable / disable EDNS version negotiation. By default EDNS version
negotiation is enabled.
+[no]ednsopt[=code[:value]]
Specify EDNS option with code point code and optionally payload of
value as a hexadecimal string. code can be either an EDNS option
name (for example, NSID or ECS), or an arbitrary numeric value.
+noednsopt clears the EDNS options to be sent.
+[no]expire
Send an EDNS Expire option.
+[no]fail
Do not try the next server if you receive a SERVFAIL. The default
is to not try the next server which is the reverse of normal stub
resolver behavior.
+[no]header-only
Send a query with a DNS header without a question section. The
default is to add a question section. The query type and query name
are ignored when this is set.
+[no]identify
Show [or do not show] the IP address and port number that supplied
the answer when the +short option is enabled. If short form answers
are requested, the default is not to show the source address and
port number of the server that provided the answer.
+[no]idnin
Process [do not process] IDN domain names on input. This requires
IDN SUPPORT to have been enabled at compile time. The default is to
process IDN input.
+[no]idnout
Convert [do not convert] puny code on output. This requires IDN
SUPPORT to have been enabled at compile time. The default is to
convert output.
+[no]ignore
Ignore truncation in UDP responses instead of retrying with TCP. By
default, TCP retries are performed.
+[no]keepalive
Send [or do not send] an EDNS Keepalive option.
+[no]keepopen
Keep the TCP socket open between queries and reuse it rather than
creating a new TCP socket for each lookup. The default is
+nokeepopen.
+[no]mapped
Allow mapped IPv4 over IPv6 addresses to be used. The default is
+mapped.
+[no]multiline
Print records like the SOA records in a verbose multi-line format
with human-readable comments. The default is to print each record
on a single line, to facilitate machine parsing of the dig output.
+ndots=D
Set the number of dots that have to appear in name to D for it to
be considered absolute. The default value is that defined using the
ndots statement in /etc/resolv.conf, or 1 if no ndots statement is
present. Names with fewer dots are interpreted as relative names
and will be searched for in the domains listed in the search or
domain directive in /etc/resolv.conf if +search is set.
+[no]nsid
Include an EDNS name server ID request when sending a query.
+[no]nssearch
When this option is set, dig attempts to find the authoritative
name servers for the zone containing the name being looked up and
display the SOA record that each name server has for the zone.
+[no]onesoa
Print only one (starting) SOA record when performing an AXFR. The
default is to print both the starting and ending SOA records.
+[no]opcode=value
Set [restore] the DNS message opcode to the specified value. The
default value is QUERY (0).
+padding=value
Pad the size of the query packet using the EDNS Padding option to
blocks of value bytes. For example, +padding=32 would cause a
48-byte query to be padded to 64 bytes. The default block size is
0, which disables padding. The maximum is 512. Values are
ordinarily expected to be powers of two, such as 128; however, this
is not mandatory. Responses to padded queries may also be padded,
but only if the query uses TCP or DNS COOKIE.
+[no]qr
Print [do not print] the query as it is sent. By default, the query
is not printed.
+[no]question
Print [do not print] the question section of a query when an answer
is returned. The default is to print the question section as a
comment.
+[no]rdflag
A synonym for +[no]recurse.
+[no]recurse
Toggle the setting of the RD (recursion desired) bit in the query.
This bit is set by default, which means dig normally sends
recursive queries. Recursion is automatically disabled when the
+nssearch or +trace query options are used.
+retry=T
Sets the number of times to retry UDP queries to server to T
instead of the default, 2. Unlike +tries, this does not include the
initial query.
+[no]rrcomments
Toggle the display of per-record comments in the output (for
example, human-readable key information about DNSKEY records). The
default is not to print record comments unless multiline mode is
active.
+[no]search
Use [do not use] the search list defined by the searchlist or
domain directive in resolv.conf (if any). The search list is not
used by default.
'ndots' from resolv.conf (default 1) which may be overridden by
+ndots determines if the name will be treated as relative or not
and hence whether a search is eventually performed or not.
+[no]short
Provide a terse answer. The default is to print the answer in a
verbose form.
+[no]showsearch
Perform [do not perform] a search showing intermediate results.
+[no]sigchase
This feature is now obsolete and has been removed; use delv
instead.
+split=W
Split long hex- or base64-formatted fields in resource records into
chunks of W characters (where W is rounded up to the nearest
multiple of 4). +nosplit or +split=0 causes fields not to be split
at all. The default is 56 characters, or 44 characters when
multiline mode is active.
+[no]stats
This query option toggles the printing of statistics: when the
query was made, the size of the reply and so on. The default
behavior is to print the query statistics.
+[no]subnet=addr[/prefix-length]
Send (don't send) an EDNS Client Subnet option with the specified
IP address or network prefix.
dig+subnet=0.0.0.0/0, or simply dig+subnet=0 for short, sends an
EDNS CLIENT-SUBNET option with an empty address and a source
prefix-length of zero, which signals a resolver that the client's
address information must not be used when resolving this query.
+[no]tcp
Use [do not use] TCP when querying name servers. The default
behavior is to use UDP unless a type any or ixfr=N query is
requested, in which case the default is TCP. AXFR queries always
use TCP.
+timeout=T
Sets the timeout for a query to T seconds. The default timeout is 5
seconds. An attempt to set T to less than 1 will result in a query
timeout of 1 second being applied.
+[no]topdown
This feature is related to dig+sigchase, which is obsolete and has
been removed. Use delv instead.
+[no]trace
Toggle tracing of the delegation path from the root name servers
for the name being looked up. Tracing is disabled by default. When
tracing is enabled, dig makes iterative queries to resolve the name
being looked up. It will follow referrals from the root servers,
showing the answer from each server that was used to resolve the
lookup.
If @server is also specified, it affects only the initial query for
the root zone name servers.
+dnssec is also set when +trace is set to better emulate the
default queries from a nameserver.
+tries=T
Sets the number of times to try UDP queries to server to T instead
of the default, 3. If T is less than or equal to zero, the number
of tries is silently rounded up to 1.
+trusted-key=####
Formerly specified trusted keys for use with dig+sigchase. This
feature is now obsolete and has been removed; use delv instead.
+[no]ttlid
Display [do not display] the TTL when printing the record.
+[no]ttlunits
Display [do not display] the TTL in friendly human-readable time
units of "s", "m", "h", "d", and "w", representing seconds,
minutes, hours, days and weeks. Implies +ttlid.
+[no]unknownformat
Print all RDATA in unknown RR type presentation format (RFC 3597).
The default is to print RDATA for known types in the type's
presentation format.
+[no]vc
Use [do not use] TCP when querying name servers. This alternate
syntax to +[no]tcp is provided for backwards compatibility. The
"vc" stands for "virtual circuit".
+[no]zflag
Set [do not set] the last unassigned DNS header flag in a DNS
query. This flag is off by default.

MULTIPLE QUERIES

The BIND 9 implementation of dig supports specifying multiple queries
on the command line (in addition to supporting the -f batch file
option). Each of those queries can be supplied with its own set of
flags, options and query options.
In this case, each query argument represent an individual query in the
command-line syntax described above. Each consists of any of the
standard options and flags, the name to be looked up, an optional query
type and class and any query options that should be applied to that
query.
A global set of query options, which should be applied to all queries,
can also be supplied. These global query options must precede the first
tuple of name, class, type, options, flags, and query options supplied
on the command line. Any global query options (except +[no]cmd and
+[no]short options) can be overridden by a query-specific set of query
options. For example:
dig +qr www.isc.org any -x 127.0.0.1 isc.org ns +noqr
shows how dig could be used from the command line to make three
lookups: an ANY query for www.isc.org, a reverse lookup of 127.0.0.1
and a query for the NS records of isc.org. A global query option of +qr
is applied, so that dig shows the initial query it made for each
lookup. The final query has a local query option of +noqr which means
that dig will not print the initial query when it looks up the NS
records for isc.org.

IDN SUPPORT

If dig has been built with IDN (internationalized domain name) support,
it can accept and display non-ASCII domain names. dig appropriately
converts character encoding of domain name before sending a request to
DNS server or displaying a reply from the server. If you'd like to turn
off the IDN support for some reason, use parameters +noidnin and
+noidnout.